That TrustedInstaller error is on the web in many prior discussions. So I'll not duplicate that answer today.
However once you expunge Flash I have some advice on how to install it again without the crapware that is so hard to avoid.
Go to ninite.com. For Flash it's not a standout but I used the checkbox Shockwave. May as well get Air too.
Here's why I go there: http://www.howtogeek.com/201354/ninite-is-the-only-safe-place-to-get-windows-freeware/
Now there are OTHER reasons for all this but the list gets rather long. My recurring run in with Hotspotshield has me calling that out. Maybe that's a good thing or maybe it's bad. All I know is that I have to eject that from time to time.
Bob
Hey cnet community,
I just bought a new Laptop (Lenovo S440), Windows 8.1 64bit, installed the Firefox web browser (35.0.1), downloaded the Adobe shockwave flash (16.0.0.305). Now I am trying to watch a YouTube video (https://www.youtube.com/watch?v=GrJlUVCe4VA) on HD 1080p and I am experiencing constant pausing and buffering (around every 30 seconds). My internet connection is above 20mbit/s, so that should not be a problem. I measured it with the Ookla online internet speed test. When watching the exact same video on my brother's computer on 1080p it works smoothly, he is connected to the same modem as I am. I do not understand why I am experiencing this issues, my Laptop has the Intel i7 processor and is new, he is using an older PC with the i3. I already tried to uninstall the Flash and Mozilla Firefox and reinstall it, but that did not help (But I could not completely remove it in the way they describe it here https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html, because I could not delete the files in C:\Windows\system32\Macromed\Flash, it said I needed permission from the TrustedInstaller to delete the files). Why is that? I also compared watching a Twitch stream on the highest quality "Source" on my laptop as well as on his computer, same story, it works smoothly for him but it keeps pausing and buffering on mine every minute or so. I really do not understand why I have this issue, as my laptop should actually be much faster than his. Another big problem is that online movie streams do not work at all, basically every other movie or video streaming website does not work for me, it just keeps buffering and loading. For example https://archive.org/details/97154_hm_eastern_homes keeps buffering for 15-20 minutes before it sometimes eventually starts, on html5 as well as on flash (you can decide which one to use under the video). What am I doing wrong? I also tried the same thing with the Internet explorer but there the same story, the movie does not start and on YouTube it keeps pausing and buffering. Could it be an issue with graphic card drivers or settings or is it the adobe flash playert? It is really frustrating because watching online media is a big part of what I bought this new expensive laptop for.
Regards and thanks for any help,
Adrian

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